1. Field of the Invention
The present invention relates to a hand-off control method in a radio communication system, and more particularly to a hand-off control method in a radio communication system for controlling the reverse-link radio wave interference between radio access terminals and accelerating hand-off.
2. Description of the Related Art
In a mobile radio communication system, it is indispensable to realize hand-off which is a process for switching the base station of a communication destination in accordance with the movement of a radio access terminal.
In the 1xEV-DO system in which a radio access terminal selects a communication destination, the radio access terminal selects a base station of the best radio quality on the basis of reception power levels from base stations, and it transmits the information of the radio quality and the information of the selected base station by using a dedicated channel called “DRC (Data Rate Control)”. It is a hand-off request that the radio access terminal alters the selected base station. When the base station of a hand-off destination designated as a new communication destination receives the hand-off request, a hand-off process is executed. In order to accelerate hand-off, therefore, it becomes important to shorten a time period which is expended until the base station of the hand-off destination receives the hand-off request.
Here, in a case where a sector having the best quality of a forward link and a sector having the best quality of a reverse link are different, the sector having the best quality of the forward link is selected as the hand-off-destination base station. However, a long time is expended on the reception of a reverse signal, with the result that a long time might be expended on the hand-off. As a technique for shortening the time period which is expended until the hand-off-destination base station receives the hand-off request, Non-patent Document 1 as follows has introduced a mechanism according to which, in a case where the base station information has been altered by the DRC channel, the transmission power of the DRC channel is increased a fixed quantity for a predetermined fixed time period, thereby to enhance a reception characteristic.
[Non-patent Document 1] 3gpp2, C. S0024B ver 1.0, cdma2000 High Rate Packet Data Air Interface Specification (corresponding pages: 10-104 to 10-125, and 10-137 to 10-165).